The lemming is a small, mouse-like rodent. The population numbers of this animal fluctuate greatly over a period of 3 to 4 years; their numbers soar, which causes the animals to leave their homes and scatter in all directions, which leads to a severe reduction in their numbers. This life cycle controls the rhythm of most animal life on the tundra. Their many predators include ermines, foxes, snowy owls, weasels, gyrfalcons, and jaegers. These small mammals live less than 2 years in the wild. There are about a dozen lemming species worldwide.

Runways: Lemmings make paths through the grass, under roots or under snow, called runways. They use these runways for shelter and for finding food.

Diet: Lemmings are herbivores (plant-eaters) who eat moss and grass.

Habitat and Range: Lemmings live in the cold tundra, woods, marshes, and meadows of northern North America and northern Eurasia.

Anatomy: Lemmings range from 3 to 6 inches (8-15 cm) long plus a very short tail. They weigh from 1/2 to 4 ounces (14-113 gm).